The present invention relates to solar energy collecting apparatus of the type including fluid circulating conduits which are exposed to the sun. More particularly, the present invention is directed to a novel method and apparatus for presenting a barrier or screen in the form of a fluid layer between the conduits and the sun to prevent the conduits from rising above a predetermined temperature.
Generally, known solar energy collecting apparatus include a bank of fluid circulating conduits which are supported in some type of mounting on a home or building. The mounting may be directed at predetermined angles relative to the sun and the conduits transport heated fluid to end uses in the home or building. A problem present with known apparatus resides in the fact that the fluid circulating conduits are generally constructed of metallic materials such as copper or copper alloys. Such materials are generally satisfactory from a heat transfer standpoint, but are relatively heavy and in large collecting apparatus result in substantial fabrication and installation costs.
It has been proposed to utilize synthetic materials for the fluid circulating conduits and coat them with black or dark material in order to increase their absorption capability. However, during warm periods such as the summer, a collecting apparatus may be shut down. Fluid may not be circulated through the conduits during such a period and the conduits can become quite hot. In the case where plastic or synthetic materials are used in the conduit construction, too much solar energy may be absorbed. The result is that the conduits will become softened and damaged. If no provision is made to limit absorption of solar energy by the exposed conduits, they may melt.
Materials such as polyvinylchloride (PVC) may become softened at around 160.degree. F. Temperatures in this range may readily occur on rooftops of homes or buildings during the summer. In order to provide an effective solar energy collecting apparatus utilizing plastic materials in the fluid circulating conduits, it is necessary to somehow limit or control the penetration of the sun's rays onto the conduits during down times.
Accordingly, it is a general object of the present invention to provide a solar intercept or fluid barrier which is automatically operable for presenting a fluid layer between the sun's rays and the fluid circulating conduits so that the conduits are inhibited from absorbing solar energy. This object is accomplished by providing spaced-apart cover plates over the conduits between the conduits and the sun's rays. The spaced-apart cover plates define an enclosed compartment which is adapted for receiving a fluid. When the compartment is filled with the fluid, the sun's rays are effectively intercepted and reflected so that they are not absorbed by the conduits.
Another object of the present invention is to provide an enclosed compartment as described above which communicates with a fluid reservoir. A control device is operatively connected to a temperature sensor which senses conduit temperature. Upon conduit temperature reaching a predetermined level, the control device opens a valve interposed between the reservoir and the compartment for permitting fluid under pressure, as by gravity or induced pressure, to fill the compartment and shield the conduits from absorbing further solar energy.
Still another object of the present invention is to provide a fluid barrier in which the control device is also operatively connected to a pump for extracting fluid from the compartment upon conduit temperature being lowered to a second predetermined temperature which is lower than the first predetermined temperature. The pump delivers fluid from the compartment back to the reservoir.
A further object of the present invention is to provide an arrangement whereby the operation of the control and transfer of the fluid from the reservoir to the compartment is automatically accomplished without requiring an external motivating mechanism.